In semiconductor fabrications, chemical mechanical polishing (CMP) is used for planarization of semiconductor wafers that may be used for the fabrication of very large scale integrated (VLSI) circuits and ultra large scale integrated (ULFI) circuits. Chemical mechanical polishing (CMP), generally, removes material from a layer of a wafer. In a typical CMP process, the wafer is exposed to an abrasive medium under controlled chemical, pressure, velocity, and temperature conditions. The abrasive medium may include slurry solutions containing small abrasive particles such as silicon dioxide and chemically reactive substances such as potassium hydroxide.
Typical chemical mechanical polishing (CMP) processes include a carrier head that holds a wafer against polishing pad. One or both of the polishing pad or carrier head may rotate to effect the polishing of the wafer. Generally, carrier heads include a retaining ring used to hold the wafer within a given boundary. In general, retaining rings are formed either completely of a metal construction or a metal backing with a ring portion of polymer or silicon dioxide. The ring portion typically contacts the polishing pad or surface and the semiconductor wafer.
Typical designs may cause damage to chip edges and surfaces. These designs may further lead to scratched wafer surfaces and altered device properties. As such, an improved CMP retaining ring would be desirable.